It is often desirable to modify the surface of a material for such purposes as making an otherwise nonwettable surface wettable, passivating the surface, making the surface more amenable to adhesive bonding, or immobilizing desired molecules onto the surface. For example, hydrophobic membranes made from polysulfone, polycarbonate or polyvinylidene difluoride can be made permanently wettable by the attachment of hydrophilic polymers. Similarly, such membranes can be "passivated" by attaching polymers that serve to prevent the adsorption of proteins or lipids that could foul the membranes.
Membranes or other porous materials can also be modified in order to immobilize binding proteins, such as antibodies or other receptors, for use as affinity purification media. Likewise, materials that are difficult to bond, such as polyolefins or silicone rubber, can be modified with a primer to allow stronger bonds to other materials. Methods have also been described for modifying surfaces by the immobilization of photopolymers. U.S. Pat. No. 5,002,582, for instance, describes such methods and is incorporated herein by reference.
On a separate subject, the term "telomerization" was originally used to describe the free radical polymerization of ethylene. Today, this word can be defined more broadly as the process of reacting, under polymerization conditions, a telogen (AB) with more than one unit of a taxogen (e.g., a polymerizable compound having ethylenic unsaturation) in order to form products called telomers. A telomer has the formula A(C).sub.n B where (C).sub.n (with "C" being called a taxomon) is a divalent radical formed by chemical union of molecules of the taxogen, n is greater than one, and A and B are fragments of the original telogen, now attached to the terminal taxomons. Telomerization can now be used to describe polymerization methods that include free radical, anionic, cationic, and transition metal catalyzed processes. See, for instance, "Telomerization", pp. 1163-1164 in Concise Encyclopedia of Polymer Science and Engineering, Kroschwitz, ed., John Wiley and Sons, 1990, the disclosure of which is incorporated herein by reference.
Polymerization processes have previously been described that include the use of compounds, known as "chain transfer agents", to control the weight of synthetic polymers. Methods for the synthesis of polymers having certain functional groups at one end have been previously reported. Takei, Y. G., et. al. Bioconj. Chem. 4:42 (1993) and Andreani, F.et.al., J. Bioactive and Compatible Polymers, 1:72 (1986) describe such methods and are incorporated herein by reference. Such polymers have been described as "telechelic", meaning a polymer having a functional endgroup such as a terminal hydroxyl, thiol, halide, carboxyl or amine group. See, e.g., "Terminally reactive oligomers: telechelic oligomers and macromers", pp. 162-196, J. Ebdon, Chapt. 6, in New Methods of Polymer Synthesis, Chapman and Hall, 1991. Alternatively, the word "semitelechelic" can be used to refer to a linear macromolecule possessing a functional group at one end of the molecule. (See, e.g., S. Kamei, et al., Pharm. Res. 12(5):663-338 (1995).
U.S. Pat. No. 5,399,642 describes latent thiol mercaptan chain transfer agents, and their use in the synthesis of polymers. The polymers have at least one protected thiol group, said to be primarily at the terminal portion of the chain. The polymer can be used with the thiol group in its protected form, or the thiol group can be deprotected to yield a terminal thiol group capable of reacting with other monomers to form a block copolymer.
U.S. Pat. No. 5,412,015 describes polymers having at least one amine sulfide terminal moiety, imparted by the use of amine-thiols as chain transfer agents. See also, Andreani et al. "Synthesis of Functionalized End-capped N-vinylpyrrolidone Telomers with Potential Utility as Drug-Binding Matricies", J. Bioactive and Compatible Polymers 1:72-78 (1986); Veronese et al., "Hydroxyl-Terminated Polyvinylpyrrolidone for the Modification of Polypeptides", J. Bioactive and Compatible Polymers, 5:167-178 (1990); and Takei et al. "Temperature Responsive Bioconjugates", Bioconjugate Chem. 4:42-46 (1993).
Applicants are unaware, however, of any art that teaches or suggests either the preparation or use of chain transfer agents to provide polymers having terminal photoactivatable groups.